Metal detector, handheld power tool comprising this metal detector, metal detection method, and metal detection program

ABSTRACT

A metal detector  20  includes a cover  25 , a detection signal acquisition unit  31 , a determination unit  32 , a display unit  24 , and a display control unit  34 . The cover  25  is removably attached to a tip portion  18  of a handheld power tool  10 . The detection signal acquisition unit  31  acquires a detection signal that changes according to the detection strength of rebar W 1  in concrete W. The determination unit  32  determines the presence or absence of the rebar W 1  on the basis of the acquisition result acquired by the detection signal acquisition unit  31 . The display unit  24  displays the presence or absence of the rebar W 1  by lighting lamps in different colors. The display control unit  34  controls so as to switch the color of the light displayed on the display unit  24  on the basis of the determination result by the determination unit  32.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No.2020-209571 filed on Dec. 17, 2020. The entire disclosure of JapanesePatent Application No. 2020-209571 is hereby incorporated herein byreference.

BACKGROUND Technical Field

The present invention relates, for example, to a metal detector thatdetects rebar or other such metal contained in concrete, as well as to ahandheld power tool including this metal detector, a metal detectionmethod, and a metal detection program.

Description of the Related Art

Recent years have seen the use of metal detectors that detect theposition of rebar or other such metal in order to perform drilling orthe like in concrete while avoiding buried targets such as rebarcontained in the concrete, for example.

Conventionally, a metal detector such as this has been used to detectrebar inside concrete, and the detection results were marked so thatdrilling could be performed, using a handheld power tool such as ahammer drill, in the concrete while avoiding the positions where therebar was embedded.

However, when using a handheld power tool at a work site where there ismuch rebar, such as a solid foundation or concrete blocks, complicatedmarking work is sometimes not performed when performing continuousdrilling work such as anchoring or coring.

In this case, a problem was that the drill would come into contact withthe rebar in the concrete during work with the handheld power tool,resulting in damage to the drill, etc.

For example, Patent Literature 1 discloses a power tool with a built-inmetal detector, wherein, when drilling a hole in a concrete surface, ifthe drill comes into contact with a metal water pipe embedded in theconcrete, an induced current is generated in an electric circuit tolight a lamp and generate a buzzer sound.

CITATION LIST Patent Literature

-   Patent Literature 1: JP-A 2000-308980

SUMMARY

However, the following problem is encountered with the above-mentionedconventional power tool having a built-in metal detector.

With the power tool disclosed in the above publication, since theoperator is notified by lighting a lamp, generating a buzzer sound,etc., after making contact with the metal in the concrete, this can leadto problems such as damage to the drill or other such tip tool thatcomes into contact with the metal, or injury to the operator's wristcaused by impact upon contact with the metal.

It is an object of the present invention to provide a metal detectorcapable of notifying an operator of the presence or absence of metalwithout making contact with the metal located inside a target such asconcrete, as well as a handheld power tool including this metaldetector, a metal detection method, and a metal detection program.

The metal detector according to the first invention is metal detectorthat detects metal contained in a target and is removably attached to ahandheld power tool that is used to work on the target, the metaldetector including a mounting portion, a detection signal acquisitionunit, a display unit, and a display control unit. The mounting portionis mounted on the distal end part of the handheld power tool. Thedetection signal acquisition unit acquires a detection signal whichchanges according to the detection intensity of the metal contained inthe target. The determination unit determines the presence or absence ofthe metal on the basis of the acquisition result acquired by thedetection signal acquisition unit. The display unit displays thepresence or absence of the metal by turning on different lights. Thedisplay control unit controls so as to switch the color of the lightdisplayed on the display unit on the basis of the determination resultfrom the determination unit.

Here, for example, it is a metal detector that is removably attached toa handheld power tool that drives a tip tool such as a drill to make ahole in a target such as concrete, wherein metal such as the rebarcontained in concrete or another such target is detected, and thisdetection result is displayed by switching the color of the light.

Here, examples of the handheld power tool to which the metal detector isattached include power tools that perform various kinds of work onconcrete or another such target while being held by an operator, such asa hammer drill, an impact drill, and a vibrating drill.

Examples of targets include concrete used at a construction site such asan apartment building, a high-rise building, or a factory, a wall madeof drywall, etc., and the like.

Also, the metal to be detected includes, for example, rebar contained inreinforced concrete, and metal such as aluminum or stainless steelinstalled in a wall.

Metal detection includes, for example, an induction type that detectsthe impedance of a detection coil which changes due to an eddy currentgenerated in the metal when the metal (what is to be detected)approaches the magnetic field generated by passing a current through thedetection coil; a capacitance type that detects a change in capacitancethat occurs between the metal to be detected and another material; and ahigh-frequency oscillation type that detects a non-ferrous metal such asaluminum.

Examples of display control according to the presence or absence ofmetal include giving a display with lamps that emit three differentcolors of light, such as lighting a lamp in red when it is determinedthat metal is nearby, lighting a lamp in green when it is determinedthat metal is not nearby, and lighting a lamp in yellow for adetermination that is in between the above two.

Consequently, when drilling a hole in concrete or another such targetwith a handheld power tool, the presence or absence of metal is detectedin a state in which the handheld power tool has been brought intocontact with the surface of the target, and the detection result isdisplayed on the display unit by switching the color of the light, sothat the operator can work on the target while keeping an eye on thecolor of the light on the display unit on which the detection result isdisplayed, and recognizing the position of the metal.

As a result, there is no need to perform marking, and the operator canbe notified of the presence or absence of metal without coming intocontact with the metal located inside the concrete or other such target,and the target can be subjected to various kinds of work.

The metal detector according to the second invention is the metaldetector according to the first invention, further comprising aprohibition signal transmission unit that transmits a drive prohibitionsignal for prohibiting drive of the handheld power tool when it has beendetermined by the determination unit that metal is present.

Consequently, if the determination unit determines that there is metal,this determination result can be reflected in the drive control of thedrive unit to prohibit drive.

This avoids problems such as when the tip of the drill comes intocontact with metal in the course of drilling or the like even though ithas been determined that there is metal present, which further improvessafety.

The metal detector according to the third invention is the metaldetector according to the first or second invention, further comprisinga permission signal transmission unit that transmits a drive permissionsignal for permitting drive of the handheld power tool when it has beendetermined by the determination unit that metal is absent.

Consequently, if the determination unit determines that there is nometal, this determination result can be reflected in the drive controlof the drive unit to allow drive.

This permits drilling or the like only when it is determined that thereis no metal, thereby avoiding problems such as the tip of the drillcoming into contact with the metal, and further improving safety.

The metal detector according to the fourth invention is the metaldetector according to any of the first to third inventions, wherein thedisplay control unit controls the display unit so as to emit anauxiliary light that illuminates the portion to be worked by the tiptool that will work the target, while the handheld power tool is beingdriven.

Consequently, when performing actual work after the determination resultfor the presence or absence of metal from the determination unit hasbeen displayed on the display unit, the light on the display unit can beused as auxiliary light that illuminates the portion being worked.

The metal detector according to the fifth invention is the metaldetector according to the fourth invention, wherein the display controlunit controls the display unit so as to emit white light as theauxiliary light.

Consequently, the light emitted from the display unit can illuminate theworked portion in white light, allowing the work to be carried out in abrightly lit state.

The metal detector according to the sixth invention is the metaldetector according to any of the first to fifth inventions, wherein thedetermination unit determines the presence or absence of metal bycomparing the acquisition result acquired by the detection signalacquisition unit with a specific threshold value.

Consequently, the determination unit can determine the presence orabsence of metal by comparing the acquisition result of the detectionsignal acquisition unit with a specific threshold value.

The metal detector according to the seventh invention is the metaldetector according to any of the first to sixth inventions, furthercomprising an orientation sensing unit that senses the orientation ofthe handheld power tool, and an initialization processing unit thatinitializes the result acquired by the detection signal acquisition unitwhen the orientation sensing unit has sensed that the handheld powertool is in a specific orientation.

Consequently, when the upward orientation of the handheld power tool isset as the specific orientation, for example, the result acquired by thedetection signal acquisition unit is reset (initialized) every time theoperator turns the handheld power tool to face upward.

Therefore, initialization processing can be performed simply by puttingthe handheld power tool in a specific orientation, without having tooperate a reset switch or the like every time the work site changes, andthis makes the tool more usable for the operator.

The metal detector according to the eighth invention is the metaldetector according to any of the first to seventh inventions, furthercomprising a contact portion having a roller portion that comes intocontact with the target and rotates in the movement direction of thehandheld power tool in a state of being in contact with the target.

Consequently, when the metal detector is brought into contact withconcrete or another such target, since a roller is provided to thecontact portion, metal detection scanning can be performed while easilymoving the handheld power tool over the surface of the target as theroller rotates.

The metal detector according to the ninth invention is the metaldetector according to any of the first to seventh inventions, furthercomprising a contact portion having a friction reducing portion thatcomes into contact with the target and reduces the friction generatedbetween the target and the contact portion.

Here, the friction reducing portion includes, for example, a portionhaving a surface treatment for reducing friction generated with a targetsuch as concrete, a shape having a reduced contact area, and the like.

Consequently, when the metal detector is brought into contact withconcrete or another such target, the surface of the target can bescanned while the handheld power tool is easily moved over the surfaceof the target.

The metal detector according to the tenth invention is the metaldetector according to any of the first to ninth inventions, furthercomprising a contact detection unit for detecting contact with thetarget.

Consequently, detecting that the handheld power tool has come intocontact with the concrete or other target makes it possible to performcontrol such as prohibiting the drive of the drive unit unless thehandheld power tool is in contact with the target.

The metal detector according to the eleventh invention is the metaldetector according to the tenth invention, wherein the contact detectionunit is a contact switch that changes from an OFF state to an ON stateupon coming into contact with the target.

This allows contact between the handheld power tool and the target to bedetected with an inexpensive configuration by using a pressing-typecontact switch as the contact detecting unit, for example.

The metal detector according to the twelfth invention is the metaldetector according to the tenth or eleventh invention, furthercomprising a retracting mechanism for retracting from the distal endpart of the handheld power tool when the contact detection unit hasdetected contact with the target.

Consequently, when it is detected that the handheld power tool has comeinto contact with the target, the metal detector is automaticallyretracted from the distal end part of the main body, which makes iteasier for the operator to see the part being worked on and also makesit less likely that dust and the like generated when the drill or othersuch tip tool is rotated to make a hole, for example, from clinging tothe metal detector.

The metal detector according to the thirteenth invention is the metaldetector according to any of the first to twelfth inventions, furthercomprising a dust collecting unit that draws in the outside air aroundthe distal end part of the handheld power tool.

Consequently, providing a dust collecting portion to the distal end partof the main body helps keep the work site clean by drawing in the dustand the like generated during drilling and so forth.

The metal detector according to the fourteenth invention is the metaldetector according to the thirteenth invention, wherein the dustcollecting unit can be removed from the distal end part of the handheldpower tool.

Consequently, since the dust collecting unit is removably attached tothe main body, the handheld power tool can be used without the dustcollecting unit when performing work that does not produce dust, at worksites where there is no problem even if dust is produced, and in othersuch work.

The handheld power tool according to the fifteenth invention comprisesthe metal detector according to any of claims 1 to 14; a distal end partto which the metal detector is mounted; a drive unit that rotationallydrives the tip tool for working the target; and a drive control unitthat controls the drive of the drive unit.

Consequently, the handheld power tool can be used in a state in whichthe metal detector is attached, so no marking work is necessary, and theoperator can be notified of the presence or absence of metal locatedinside the concrete or other such target, without any contact with themetal being made, and various kinds of work can be performed on thetarget.

The metal detection method that makes use of a metal detector accordingto the sixteenth invention is a method that makes use of a metaldetector that detects metal contained in a target and is removablyattached to the distal end part of a handheld power tool that is used towork on the target, the method comprising a detection signal acquisitionstep, a determination step, and a display control step. In the detectionsignal acquisition step, a detection signal acquisition unit of themetal detector acquires a detection signal that changes according to thedetection intensity of the metal in the target. In the determinationstep, a determination unit of the metal detector determines the presenceor absence of the metal on the basis of the acquisition result acquiredby the detection signal acquisition unit. In the display control step, adisplay control unit of the metal detector controls so as to switch thecolor of the light displayed on the display unit on the basis of thedetermination result by the determination unit.

Here, for example, it is a metal detection method that makes use of ametal detector that is removably attached to a handheld power tool thatdrives a tip tool such as a drill to make a hole in a target such asconcrete, wherein metal such as the rebar contained in concrete oranother such target is detected, and this detection result is displayedby switching the color of the light.

Here, examples of the handheld power tool to which the metal detector isattached include power tools that perform various kinds of work onconcrete or another such target while being held by an operator, such asa hammer drill, an impact drill, and a vibrating drill.

Examples of targets include concrete used at a construction site such asan apartment building, a high-rise building, or a factory, a wall madeof drywall, etc., and the like.

Also, the metal to be detected includes, for example, rebar contained inreinforced concrete, and metal such as aluminum or stainless steelinstalled in a wall.

Metal detection includes, for example, an induction type that detectsthe impedance of a detection coil which changes due to an eddy currentgenerated in the metal when the metal (what is to be detected)approaches the magnetic field generated by passing a current through thedetection coil; a capacitance type that detects a change in capacitancethat occurs between the metal to be detected and another material; and ahigh-frequency oscillation type that detects a non-ferrous metal such asaluminum.

Examples of display control according to the presence or absence ofmetal include giving a display with lamps that emit three differentcolors of light, such as lighting a lamp in red when it is determinedthat metal is nearby, lighting a lamp in green when it is determinedthat metal is not nearby, and lighting a lamp in yellow for adetermination that is in between the above two.

Consequently, when drilling a hole in concrete or another such targetwith a handheld power tool, the presence or absence of metal is detectedin a state in which the handheld power tool has been brought intocontact with the surface of the target, and the detection result isdisplayed on the display unit by switching the color of the light, sothat the operator can work on the target while keeping an eye on thecolor of the light on the display unit on which the detection result isdisplayed, and recognizing the position of the metal.

As a result, there is no need to perform marking, and the operator canbe notified of the presence or absence of metal without coming intocontact with the metal located inside the concrete or other such target,and the target can be subjected to various kinds of work.

The metal detection program according to the seventeenth invention is ametal detection program that causes a computer to execute a metaldetection method that makes use of a metal detector that is removablyattached to the distal end part of a handheld power tool that willperform work inside a target, the method comprising a detection signalacquisition step in which a detection signal acquisition unit of themetal detector acquires a detection signal that changes according to thedetection intensity of the metal in the target, a determination step inwhich a determination unit of the metal detector determines the presenceor absence of the metal on the basis of the acquisition result acquiredby the detection signal acquisition unit, and a display control step inwhich a display control unit of the metal detector controls so as toswitch the color of the light displayed on the display unit on the basisof the determination result by the determination unit.

Here, for example, it is a metal detection program for a metal detectorthat is removably attached to a handheld power tool that drives a tiptool such as a drill to make a hole in a target such as concrete,wherein metal such as the rebar contained in concrete or another suchtarget is detected, and this detection result is displayed by switchingthe color of the light.

Here, examples of the handheld power tool to which the metal detector isattached include power tools that perform various kinds of work onconcrete or another such target while being held by an operator, such asa hammer drill, an impact drill, and a vibrating drill.

Examples of targets include concrete used at a construction site such asan apartment building, a high-rise building, or a factory, a wall madeof drywall, etc., and the like.

Also, the metal to be detected includes, for example, rebar contained inreinforced concrete, and metal such as aluminum or stainless steelinstalled in a wall.

Metal detection includes, for example, an induction type that detectsthe impedance of a detection coil which changes due to an eddy currentgenerated in the metal when the metal (what is to be detected)approaches the magnetic field generated by passing a current through thedetection coil; a capacitance type that detects a change in capacitancethat occurs between the metal to be detected and another material; and ahigh-frequency oscillation type that detects a non-ferrous metal such asaluminum.

Examples of display control according to the presence or absence ofmetal include giving a display with lamps that emit three differentcolors of light, such as lighting a lamp in red when it is determinedthat metal is nearby, lighting a lamp in green when it is determinedthat metal is not nearby, and lighting a lamp in yellow for adetermination that is in between the above two.

Consequently, when drilling a hole in concrete or another such targetwith a handheld power tool, the presence or absence of metal is detectedin a state in which the handheld power tool has been brought intocontact with the surface of the target, and the detection result isdisplayed on the display unit by switching the color of the light, sothat the operator can work on the target while keeping an eye on thecolor of the light on the display unit on which the detection result isdisplayed, and recognizing the position of the metal.

As a result, there is no need to perform marking, and the operator canbe notified of the presence or absence of metal without coming intocontact with the metal located inside the concrete or other such target,and the target can be subjected to various kinds of work.

(Effects)

The metal detector according to the present invention allows an operatorto be notified of the presence or absence of metal located insideconcrete or another such target without coming into contact with themetal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an oblique view of a state in which concrete is worked with ahandheld power tool equipped with the metal detector according to anembodiment of the present invention, while the presence or absence ofrebar is detected;

FIG. 2 is an overall oblique view of the configuration of the handheldpower tool in

FIG. 1;

FIG. 3 is an overall oblique view of the configuration of the handheldpower tool in

FIG. 2;

FIG. 4 is an exploded oblique view of the handheld power tool in FIG. 2;

FIG. 5 is an exploded oblique view of the handheld power tool in FIG. 3;

FIG. 6 is an exploded oblique view of the configuration of the metaldetector provided to the handheld power tool in FIG. 2, etc.;

FIG. 7 is a graph of the metal detection modes that can be set in thehandheld power tool in FIG. 2, etc.;

FIG. 8 is a control block diagram of the handheld power tool in FIG. 2,etc.;

FIG. 9 is a diagram illustrating a metal detection method using thehandheld power tool in FIG. 2, etc.;

FIGS. 10A to 10F are diagrams showing control for displaying differentcolors of light on the display unit of the metal detector in FIG. 6according to the determination result indicating the presence or absenceof metal;

FIGS. 11A to 11H are diagrams showing control for displaying differentcolors of light on the display unit of the metal detector in FIG. 6according to the determination result indicating the presence or absenceof metal;

FIGS. 12A to 12D are diagrams showing control for displaying differentcolors of light on the display unit of the metal detector in FIG. 6according to the determination result indicating the presence or absenceof metal;

FIG. 13 is a main flowchart showing the flow of processing in a metaldetection method and processing method using the handheld power tool inFIG. 1;

FIG. 14 is a flowchart showing the detailed flow of the initializationprocessing in FIG. 13;

FIG. 15 is a flowchart showing the detailed flow of the maximum valueand minimum value save processing in FIG. 13;

FIG. 16 is an oblique view of the configuration of a handheld power toolincluding the metal detector according to another embodiment of thepresent invention;

FIG. 17 is an exploded oblique view of the handheld power tool in FIG.16;

FIGS. 18A and 18B are side views illustrating a retracting mechanismincluded in the handheld power tool in FIG. 16;

FIG. 19 is a control block diagram of the handheld power tool in FIG.16;

FIGS. 20A, 20B, and 20C are oblique views of the configuration of themetal detector according to another embodiment of the present invention;and

FIG. 21 is an oblique view of a state in which the metal detector inFIG. 6 is used alone.

DETAILED DESCRIPTION Embodiment 1

A handheld power tool 10 including a metal detector 20 according to anembodiment of the present invention will now be described with referenceto FIGS. 1 to 15 and FIG. 21. In the following description, the distalend side means the side on which a tip tool 18 a for machining with thehandheld power tool 10 is mounted, and the rear end side means theopposite side from the distal end side.

As shown in FIG. 1, the handheld power tool 10 according to thisembodiment is, for example, a hammer drill (a type of handheld powertool) for performing work while the position of rebar (metal) embeddedin the concrete (target) W is detected in a state in which the tool isbeing held by the operator, the metal detector 20 is integrally attachedon the tip portion 18 side to which a tip tool 18 a such as a drill hasbeen mounted.

As shown in FIG. 1, the handheld power tool 10 moves the metal detector20 over the surface of the concrete W, and when the position where therebar W1 is embedded is approached, the operator is notified of thepresence or absence of the rebar W1 by changing the color of the lightthat appears on a display unit 24 (see FIG. 6 and the like; discussedbelow).

Consequently, the operator can recognize the presence or absence of therebar W1 by looking at the color of the light on the display unit 24.This allows drilling or other such work to be performed on the concreteW with the handheld power tool 10 while avoiding contact of the tip tool18 a with the rebar W1.

In this embodiment, an example is given in which a plurality of rebarsW1 are embedded in the concrete W in a grid pattern, but the number,thickness, length, etc., of the rebar W1 are not limited to what isshown in FIG. 1.

Here, first, the outward configuration of the handheld power tool 10will be described with reference to FIGS. 2 to 5.

As shown in FIGS. 2 and 3, the handheld power tool 10 includes a mainbody 11, the metal detector 20, and a dust collecting unit 40.

The main body 11 has a grip portion 11 a that is gripped by an operatorduring work, a trigger switch 12 a that rotationally drives a motor(drive unit) 14 (see FIG. 8) when gripped by the operator, a battery 17a that supplies the electric power for the handheld power tool 10, and atip portion 18 that is disposed on the side that does the work on theconcrete W.

As shown in FIGS. 2 and 3, the grip portion 11 a is provided so as toproject from the left side surface of the main body 11, and is grippedby the left hand of the operator when performing work with the handheldpower tool 10.

The grip portion 11 a may be attached to the operator on the oppositeside depending on the dominant hand of the operator.

Also, as shown in FIG. 3, a reset switch 19, which is pressed when themetal detector 20 is manually initialized, is provided on the front ofthe grip portion 11 a.

As shown in FIG. 2, the trigger switch 12 a is provided on the oppositeside from the tip portion 18 (the rear end side) of the main body 11,and when the tip tool 18 a is rotated to perform the work, this switchis gripped by the operator.

The battery 17 a is a rechargeable secondary battery that supplies powerto the components included in the handheld power tool 10, and isattached, so as to be replaceable, at the lower portion of the main body11 on the rear end side, as shown in FIGS. 2 and 3.

As shown in FIGS. 2 and 3, the tip portion 18 is provided on the side ofthe main body 11 closer to the concrete W during work, and a tip tool 18a such as a drill is attached to the tip portion 18. The tip portion 18is rotationally driven along with the tip tool 18 a by controlling therotational drive of the motor 14 according to how much the triggerswitch 12 a is operated.

The metal detector 20 is attached in an integrated state on the distalend side of the main body 11 of the handheld power tool 10 in order todetect the presence or absence of the rebar W1 in the concrete W onwhich work such as drilling is to be performed with the handheld powertool 10. As shown in FIGS. 4 and 5, the metal detector 20 is removablyattached to a recess formed on the rear end side of a detectorattachment unit 43 of the dust collecting unit 40.

The metal detector 20 has a substantially annular shape, and a workhole, into which the tip tool 18 a such as a drill is inserted duringmachining, is provided in the central portion thereof.

The configuration of the metal detector 20 will be described in detailbelow.

The dust collecting unit 40 is provided for sucking up the dust of theconcrete W produced when the tip tool 18 a such as a drill isrotationally driven to drill a hole in the concrete W, for example. Morespecifically, dust and the like are sucked up through a suction port 43a provided to the detector attachment unit 43, which is where the metaldetector 20 is mounted at a position on the distal end side of thehandheld power tool 10.

As shown in FIGS. 4 and 5, the dust collecting unit 40 is removablyattached to the lower part of the main body 11 of the handheld powertool 10, and has a main body 41, a mounting unit 42, the detectorattachment unit 43, and an arm portion 44.

The main body 41 has a boxy shape including a suction mechanism (notshown) inside, and a space is formed for collecting dust and the likesucked in through the suction port 43 a via the arm portion 44. The mainbody 41 is provided with the detector attachment unit 43 and the armportion 44 on the front end side where work is performed, and with themounting unit 42 on the rear end side.

As shown in FIG. 5, the mounting unit 42 is the portion of the handheldpower tool 10 to which the main body 11 is mounted, and is fixed in astate of being engaged with the main body 11.

As shown in FIGS. 4 and 5, the detector attachment unit 43 is asubstantially annular portion provided at the distal end of the armportion 44 provided on the distal end side of the main body 41 of thedust collecting unit 40, and the metal detector 20 is attached from therear end side. The detector attachment unit 43 has the suction port 43 aformed in the inner peripheral surface of a substantially annularportion.

The detector attachment unit 43 also has an opening 43 b, which servesas a work hole into which the tip tool 18 a such as a drill is inserted,in the central portion of the substantially annular ring.

Furthermore, a contact surface 46 (see FIG. 2), which comes into contactwith the concrete W during the work of detecting the rebar W1 with themetal detector 20, is formed on the distal end side of the detectorattachment unit 43.

As shown in FIG. 2, four rollers 46 a are rotatably attached to thecontact surface 46 so as to surround the central opening (work hole) ofthe detector attachment unit 43.

Consequently, the metal detector 20 can be smoothly moved in thescanning direction (for example, the lateral direction) in a state inwhich the contact surface 46 is in contact with the surface of theconcrete W. This allows metal detection to be performed while moving themetal detector 20 (handheld power tool 10) in the desired scanningdirection without producing frictional resistance between the surface ofthe concrete W and the contact surface 46.

The arm portion 44 is a member that is hollow inside, and guides dustand the like sucked up through the suction port 43 a of the detectorattachment unit 43 provided on the distal end side into the main body41. Also, the arm portion 44 is attached to the main body 41 in a statethat allows its movement forward and backward.

This allows the length of the arm portion 44 to be adjusted such thatthe length will be appropriate for the length of the tip tool 18 amounted on the tip portion 18, for example. Also, when only the work ofdetecting the presence or absence of the rebar W1 with the metaldetector 20 is performed before drilling or other such work, or when thetip tool 18 a is attached to or detached from the tip portion 18, etc.,the work of detecting the rebar W1 and the work of replacing the tiptool 18 a can be performed more easily by pulling out the arm portion 44from the main body 41.

Next, the configuration of the metal detector 20 will be described withreference to FIG. 6.

As shown in FIG. 6, the metal detector 20 has a substantially annularshape, and has a case (mounting unit) 21, a detector unit 22, a spacer23, a display unit 24, and a cover 25.

As shown in FIG. 5, the case (mounting unit) 21 is disposed on the sidewhere the metal detector 20 is mounted in the recess of the detectorattachment unit 43. As shown in FIG. 6, the case 21 is a substantiallyannular member disposed on the most distal end side among the membersconstituting the metal detector 20, and has a main body 21 a and aswitch cover 21 b.

The main body 21 a is a substantially annular member having an openingin the center, and includes the detector unit 22, the spacer 23, and thedisplay unit 24 in a space formed between the main body 21 a and thecover 25.

The switch cover 21 b is, for example, a rubber member that is attachedto the outer peripheral surface of the main body 21 a, and forms adust-proof and drip-proof structure that covers an initialization switch(not shown), etc., provided inside the main body 21 a.

Then, when a portion of the switch cover 21 b is pressed, the detectionsignal of the metal detector 20 can be initialized.

As shown in FIG. 6, the detector unit 22 has a substantially annularmain body 22 a and a coil 22 b that is wound around the outer peripheralsurface of the main body 22 a. The detector unit 22 is an induction typethat detects the rebar W1 by sensing the impedance of a coil, whichchanges due to the eddy current generated in the rebar W1 when the rebarW1 approaches the magnetic field formed when a current is passed throughthe coil 22 b.

As shown in FIG. 6, the spacer 23 has a substantially annular main body23 a, and is provided between the detector unit 22 and the substrate 24a of the display unit 24.

Consequently, the spacer 23 can reduce the metal influence of thesubstrate 24 a on the detector unit 22, and make it less likely thatheat generated in the substrate 24 a will be transferred to the detectorunit 22.

As shown in FIG. 6, the display unit 24 has a substrate 24 a, eightfull-color LEDs (light emitting diodes) 24 b, and a USB (universalserial bus) connector 24 c. The eight full-color LEDs 24 b are disposedon the substantially annular substrate 24 a, facing toward the openingformed in the center of the substrate 24 a. The LEDs 24 b notify theoperator of the detection result for the rebar W1 detected by thedetector unit 22, by turning on lights of different colors (green,yellow, and red in this embodiment) according to the distance to therebar W1.

For instance, if the distance to the rebar W1 is relatively long, thedisplay unit 24 lights the LEDs 24 b with green light. On the otherhand, if the distance to the rebar W1 is relatively short, the displayunit 24 lights the LEDs 24 b with red light. Furthermore, if thedistance to the rebar W1 is between when the green and red lights arelit, the display unit 24 causes the LEDs 24 b to emit yellow light.

With the metal detector 20 in this embodiment, since the display unit 24includes eight LEDs 24 b, all eight LEDs 24 b may be lit in the samelighting color, or the numbers of green, yellow, and red lights may beswitched depending on the distance to the rebar W1.

Consequently, the operator can recognize the approximate distance to therebar W1 by checking the color of the lights on the display unit 24 ofthe metal detector 20.

Furthermore, with the metal detector 20 in this embodiment, if it isdetermined that there is no rebar W1 as a result of detection by thedetector unit 22, for example, it is detected that the trigger switch 12a has been operated after the LEDs 24 b are lit in green, and the LEDs24 b are lit in white.

This white light is used as auxiliary light that brightly illuminatesthe position where work is to be performed when the trigger switch 12 ais operated to rotate the motor 14 and the tip tool 18 a is rotationallydriven.

Consequently, the display unit 24 can not only show the detection resultof the rebar W1 but also turn on an auxiliary light that brightlyilluminates the work position when the work is being performed.

As shown in FIG. 21, one end of a USB cable 51 for connecting to anexternal device such as a battery 50 is connected to the USB connector24 c. As a result, the metal detector 20 can be used alone by receivingpower from the battery 50 to which the other end of the USB cable 51 isconnected.

As shown in FIG. 21, the USB cable 51 may be provided with aninitialization switch 52 near the middle of the cable. As a result, theinitialization processing of the metal detector 20 can also be performedwhen the initialization switch 52 provided on the USB cable 51 isoperated.

As shown in FIG. 6, the cover 25 is a substantially annular member thatis disposed on the rearmost end side among the members constituting themetal detector 20, and together with the above-mentioned case 21,constitutes the outer shell of the metal detector 20. The cover 25 alsohas a main body 25 a and a mode display surface 25 b.

The main body 25 a is a substantially annular member, and three LEDsused for mode notification (not shown) are mounted in the interiorthereof.

The mode display surface 25 b is a surface on the rear end side(operator side) of the main body 25 a, and displays a plurality of metaldetection modes (discussed below) by turning on lights of differentcolors.

Here, in this embodiment, as shown in FIG. 7, three metal detectionmodes (deep mode, medium mode, and shallow mode) selected in advance bythe operator are set.

In the three metal detection modes, different threshold values fordetermination are set according to, for example, the depth at which therebar W1 is thought to exist, the thickness of the rebar W1, the numberof rebars, the spacing, and so forth, and the mode is selected by theoperator. Switching between these three modes is performed with a modeswitch (not shown).

Since a different threshold value is thus set for each mode, if theshallow mode is selected, for example, it is possible to improve thedetection accuracy for the rebar W1 located at a relatively shallowdepth from the surface of the concrete W. This allows a plurality ofthick rebars W1 located at a relatively shallow depth from the surfaceof the concrete W to be detected with high accuracy, for example.

Also, when the deep mode is selected, the detection accuracy of therebar W1 located at a relatively deep position from the surface of theconcrete W can be improved. This allows for better accuracy in detectingthin rebar W1 located at a greater depth from the surface of theconcrete W, for example.

The control blocks of the handheld power tool 10 will now be describedwith reference to FIG. 8.

As described above, the handheld power tool 10 includes the main body11, the metal detector 20, and the dust collecting unit 40.

As shown in FIG. 8, the main body 11 has an operation unit 12, a drivecontrol unit 13, a motor (drive unit) 14, a signal transmission andreception unit 15, an orientation sensing unit 16, a power supply unit17, and a reset switch 19.

The operation unit 12 is connected to the trigger switch 12 a of thehandheld power tool 10, detects how much the trigger switch 12 a hasbeen operated, and transmits this amount to the drive control unit 13.

The drive control unit 13 controls the rotation speed of the motor 14according to the operation amount of the trigger switch 12 a receivedfrom the operation unit 12. Also, the drive control unit 13 receives adrive prohibition signal or a drive permission signal transmitted fromthe signal transmission and reception unit 36 according to thedetermination result by the determination unit 32 of the metal detector20, and either prohibits or permits the drive of the motor 14.

The drive of the motor (drive unit) 14 is controlled by the drivecontrol unit 13, and the tip portion 18 to which the tip tool 18 a ismounted is rotationally driven to perform drilling or other such work onthe surface of the concrete W.

The signal transmission and reception unit 15 can communicate with thesignal transmission and reception unit 36 on the metal detector 20 side,receives the determination result or the like from the determinationunit 32 of the metal detector 20, and transmits this result to the drivecontrol unit 13. When the reset switch 19 provided on the main body 11side is operated, or when the orientation sensing unit 16 senses thatthe handheld power tool 10 is in a predetermined orientation, the signaltransmission and reception unit 15 sends an initialization signal forinitializing the metal detector 20 to the metal detector 20 side.

The orientation sensing unit 16 is, for example, a gyro sensor providedfor sensing that the handheld power tool 10 is in a predeterminedorientation. The orientation sensing unit 16 senses, for example, thatthe handheld power tool 10 has moved from a lateral orientation to avertical, upward-facing orientation.

With the handheld power tool 10 in this embodiment, the initializationprocess is automatically performed, for example, by sensing a specificorientation of the handheld power tool 10 in this way.

That is, the initialization processing for initializing the detectionresult from the metal detector 20 may be performed not only upon manualoperation of the reset switch 19, but also when the orientation sensingunit 16 senses that the handheld power tool 10 is in a specificorientation.

Consequently, the operator does not have to manually press the resetswitch 19 every time the place where metal is to be detected changes,for example, so the operator only needs to put the handheld power tool10 in a specific orientation when initialization is to be performed, andthe initialization processing can be automatically performed to detectthe rebar W1 and perform work at a new location.

The power supply unit 17 supplies electric power from theabove-mentioned rechargeable battery 17 a, and also supplies power tothe components inside the main body 11, to the components of the metaldetector 20, and to the dust collecting unit 40.

The reset switch 19 is a manual switch that is provided at the baseportion of the above-mentioned grip portion 11 a and is pressed when theinitialization processing of the metal detector 20 is performed. Forexample, this switch is operated by the thumb of the operator's lefthand.

As shown in FIG. 8, the metal detector 20 has a detection signalacquisition unit 31, a determination unit 32, a memory unit 33, adisplay control unit 34, a display unit 24, a signal transmission andreception unit (prohibition signal transmission unit, permission signaltransmission unit) 36, an initialization processing unit 37.

The detection signal acquisition unit 31 acquires a detection signalindicating a change in the impedance of the coil 22 b detected by thedetector unit 22 in FIG. 6.

The determination unit 32 determines the presence or absence of therebar W1 or the approximate distance to the rebar W1 on the basis of thedetection signal acquired by the detection signal acquisition unit 31.

More specifically, as shown in FIG. 9, when the metal detector 20 isscanned from left to right in the drawing in order to detect thepresence of absence of the rebar W1 embedded in the concrete W, forexample, the determination unit 32 moves the detection value up and downalong with the movement of the metal detector 20.

At this point, the determination unit 32 detects the presence or absenceof the rebar W1 by using a determination threshold value set accordingto each of the above-mentioned modes.

For example, FIG. 9 shows a composite detection graph in which peaks ofdetected values appear continuously because of a plurality of rebars W1embedded in the concrete W.

In the graph shown in FIG. 9, it is determined that the rebar W1 ispresent at the position where the detected value becomes larger than aspecific threshold value.

The memory unit 33 stores the detection signal acquired by the detectionsignal acquisition unit 31, the determination result of thedetermination unit 32, and the like.

The display control unit 34 controls the display unit 24 so as to changethe lighting colors of the eight LEDs 24 b included in theabove-mentioned display unit 24 on the basis of the determination resultby the determination unit 32.

For example, the display control unit 34 lights the eight LEDs 24 b ingreen in the initial state or when it is determined that there is norebar W1, and as the rebar W1 is approached, the color of the light ischanged from green to yellow to red, according to the distance to therebar W1.

Furthermore, when no rebar W1 is detected and the trigger switch 12 a isin its ON state, the display control unit 34 lights the eight LEDs 24 bin white, so that the work surface of the concrete W is illuminated withwhite light to assist in the work.

More precisely, in the graph shown in FIG. 9, the display control unit34 changes the lighting color of the LEDs 24 b of the display unit 24 onthe basis of the determination result by the determination unit 32, andthis notifies the operator whether the current position is one wherethere is no rebar W1.

For example, FIGS. 10A to 12D show the control for switching thelighting color of the LEDs 24 b of the display unit 24 according to thedetermination result by the determination unit 32.

That is, FIG. 10B shows the display in the initial state or when thereis no rebar W1 nearby, and shows a state in which all eight of the LEDs24 b of the display unit 24 have been lit in green.

FIG. 10A shows a state in which white light is emitted for use duringwork after the initial state in FIG. 10B, etc.

From the initial state in FIG. 10B to FIGS. 10C to 10 e, the lightingcolor of from one to three of the eight LEDs 24 b is changed from greento yellow in order to notify the operator that the tool is moving closerto the rebar W1, but that this area is one in which drilling or othersuch work can still be performed.

More specifically, in the lighting state shown in FIG. 10C the one atthe very bottom is yellow while the others are green, in the lightingstate shown in FIG. 10D the one at the very bottom and the one to theright are yellow while the others are green, and in the lighting stateshown in FIG. 10E the one at the very bottom and the two to the rightare yellow while the others are green.

The operator can preset the lit areas shown in FIGS. 10B to 10E as areasin which drilling or other such work can be performed.

Next, FIG. 10F shows the state in which the rebar W1 is now closer andthe lighting color of four of the eight LEDs 24 b has changed from greento yellow (the one at the very bottom and the three to the right areyellow while the others are green).

Consequently, the operator can set the lit area shown in FIG. 10F as anarea where work is not possible.

Similarly, FIGS. 11A to 11D show the state in which the rebar W1 is noweven closer, and the lighting color ranges from when five of the eightLEDs 24 b are yellow (the five from the very bottom to the very top areyellow while the rest are green), to when all eight of the LEDs 24 b areyellow.

Consequently, the operator can similarly set the lit areas shown inFIGS. 11A to 11D as areas in which work is not possible.

As the rebar W1 approaches even nearer, as shown in FIGS. 11E to 11H,the lighting color of from one to three of the eight LEDs 24 b changesfrom yellow to red.

More specifically, in the lighting state shown in FIG. 11E, the one atthe very bottom is red while the others are yellow, in the lightingstate shown in FIG. 11F, the one at the very bottom and the one to theright are red while the others are yellow, in the lighting state shownin FIG. 11G, the one at the very bottom and the two to the right are redwhile the others are yellow, and in the lighting state shown in FIG.11H, the one at the very bottom and the three to the right are red whilethe others are yellow.

The operator can preset the areas in the lighting state shown in FIGS.11E to 11H as areas where drilling or other such work is not possible.

As the rebar W1 approaches even nearer from here, as shown in FIGS. 12Ato 12D, the lighting color of from five to all eight of the LEDs 24 bchanges from yellow to red.

Consequently, the operator can set the areas in the lighting statesshown in FIGS. 12A to 12D as areas in which the distance from the rebarW1 is particularly short and work is therefore not possible.

With the handheld power tool 10 in this embodiment, the operator cancheck the lighting color displayed on the display unit 24, which changeson the basis of the detection result for the rebar W1 in the metaldetector 20, and can designate areas where drilling or other such workis possible (areas without rebar W1) on the basis of the detectionresult. This means that the operator can safely carry out the work whilepreventing the tip tool 18 a from coming into contact with rebar W1during the work.

As described above, the signal transmission and reception unit 36 cancommunicate with the signal transmission and reception unit 15 on themain body 11 side of the handheld power tool 10, and transmits thedetermination result of the determination unit 32 of the metal detector20, etc. Also, the signal transmission and reception unit 36 receivesfrom the main body 11 side an initialization signal for theinitialization processing of the metal detector 20 when the reset switch19 provided on the main body 11 side is operated, or when theorientation sensing unit 16 senses a specific orientation.

The initialization processing unit 37 performs initialization processingto erase the detection result of the rebar W1 stored in the memory unit33 as a result of sensing of the orientation of the handheld power tool10 by the orientation sensing unit 16, or by operation of the resetswitch 19.

Working Method using Handheld Power Tool 10 (Metal Detection Method)

With the working method using the handheld power tool 10 in thisembodiment, processing is performed according to the flowcharts shown inFIGS. 13 to 15 with the above configuration.

FIG. 13 shows the main flow, including initialization processing anddetermination processing performed in the handheld power tool 10.

That is, in step S11, when the power is turned on or the reset switch 19is pressed, for example, initialization processing is performed by theinitialization processing unit 37 of the metal detector 20 describedabove. More specifically, the initialization processing unit 37 performsinitialization processing to erase the detection signal anddetermination result stored in the memory unit 33 of the metal detector20.

At this point, the display control unit 34 lights the LEDs 24 b of thedisplay unit 24 in green to indicate the initial state shown in FIG.10B.

Next, in step S12, the determination unit 32 of the metal detector 20performs determination processing to determine whether or not there isrebar W1 at the position scanned by the metal detector 20.

At this point, the display control unit 34 lights the LEDs 24 b of thedisplay unit 24 in either green, yellow, or red corresponding to thedetermination result by the determination unit 32 (see FIGS. 10B to12D).

Next, in step S13, it is determined whether or not the reset switch 19has been operated to be in the ON state, and if it is ON, the processinggoes back to step S11 and initialization processing is performed againto determine metal detection at another location, for example.

On the other hand, if the reset switch 19 is not in its ON state, theprocessing goes back to step S12, and the determination of metaldetection at the same location, for example, is continuously performedwithout performing the initialization processing.

FIG. 14 shows the detailed flow of processing in the initializationprocessing of step S11 in FIG. 13.

That is, in step S21, the coil 22 b of the detector unit 22 beginsoscillating in order to acquire a detection signal for the rebar W1 in astate in which the metal detector 20 is in contact with the surface ofthe concrete W where the rebar W1 is to be detected.

Next, in step S22, the detection signal acquisition unit 31 of the metaldetector 20 acquires Rp data (detection signal) indicating the degree towhich the rebar W1 has been detected.

Next, in step S23, the acquired Rp data is stored in the memory unit 33as an initial Rp value (reference value), and the initializationprocessing is ended.

FIG. 15 shows the detailed flow of processing of the determinationprocessing in step S12 of FIG. 13.

That is, in step S31, in order to commence the detection of the rebarW1, the coil 22 b of the detector unit 22 begins to oscillate in a statein which the metal detector 20 is in contact with the surface of theconcrete W where the rebar W1 is to be detected, and the detectionsignal acquisition unit 31 acquires Rp data from the detector unit 22.

Next, in step S32, it is determined whether or not the difference (Rpvalue−initial Rp value) between the Rp value of the Rp data acquired instep S31 and the initial Rp value stored in the memory unit 33 in step23 is smaller than a specific threshold value.

If this difference is smaller than the threshold value, the processingproceeds to step S33, but if the difference is greater than or equal tothe threshold value, the processing proceeds to step S39.

Next, in step S33, since it was determined in step S32 that (Rpvalue−initial Rp value)<threshold value, the determination unit 32determines that there is no rebar W1.

Next, in step S34, since it was determined in step S33 that there was norebar W1, that area is determined to be an area in which drive ispermitted, and the LEDs 24 b of the display unit 24 are lit in green.

Next, in step S35, based on the determination result from thedetermination unit 32 of the metal detector 20, the signal transmissionand reception unit 36 sends the main body 11 a drive permission signal(High) for permitting the drive of the motor 14 of the main body 11.

On the other hand, in step S36, since it was determined in step S32 that(Rp value−initial Rp value)<threshold value, the determination unit 32determines that rebar W1 is present.

Next, in step S37, since it was determined in step S36 that there wasrebar W1, that area is determined to be an area in which drive isprohibited, and the LEDs 24 b of the display unit 24 are lit in red.

Regarding the green lighting control in step S34 and the red lightingcontrol in step S37, the lights may be lit to yellow in between thegreen light and the red light according to the distance to the rebar W1(the magnitude of the Rp value).

Next, in step S38, based on the determination result from thedetermination unit 32 of the metal detector 20, the signal transmissionand reception unit 36 sends the main body 11 a drive prohibition signal(Low) for prohibiting the driving of the motor 14 of the main body 11.

Next, in step S39, the signal transmission and reception unit 15 on themain body 11 side receives a determination signal (drive permissionsignal (High) or drive prohibition signal (Low)) from the signaltransmission and reception unit 36 on the metal detector 20 side.

Next, in step S40, when the trigger switch 12 a is operated to the ONposition, it is determined in step S41 whether or not the receiveddetermination signal is a drive permission signal (High).

Here, if the determination signal received by the signal transmissionand reception unit 15 is a drive permission signal (High), theprocessing proceeds to step S42. On the other hand, if the receiveddetermination signal is a drive prohibition signal (Low), the processingproceeds to step S45.

Next, in step S42, since the determination signal received by the signaltransmission and reception unit 15 was determined in step S41 to be adrive permission signal (High), the drive control unit 13 permits driveof the motor 14.

Next, in step S43, the signal transmission and reception unit 36transmits a drive permission signal, and in step S36, the trigger switch12 a is operated to the ON position, so the display control unit 34lights the LEDs 24 b of the display unit 24 in white.

Next, in step S44, the drive control unit 13 controls the rotation speedof the motor 14 according to how much the trigger switch 12 a has beenoperated, to rotationally drive the tip tool 18 a.

Consequently, the operator can carry out the work in a state in whichthe worksite portion is brightly illuminated by white light when theconcrete W is being worked while avoiding the rebar W1.

As a result, the work is easier and safer for the operator.

On the other hand, in step S45, since it was determined in step S41 thatthe determination signal received by the signal transmission andreception unit 15 was not a drive permission signal (High), the signaltransmission and reception unit 15 is determined to have received adrive prohibition signal (Low), the drive of the motor 14 is notpermitted, and the processing is ended.

Consequently, the drive control unit 13 can control not to drive themotor 14 by prohibiting the drive of the motor 14 on the main body 11side, even if the trigger switch 12 a is operated to the ON position ina drive prohibition area, when it has been determined that rebar W1 isin a drive prohibition area in step 39.

As a result, the tip tool 18 a can be prevented from coming into contactwith the rebar W1 due to accidental work in a drive prohibition areaincluding rebar W1.

Also, with the handheld power tool 10 in this embodiment, since themetal detector 20 is provided on the distal end side, the concrete W canbe worked while avoiding the rebar W1 and while performing theprocessing to detect the rebar W1.

This means that there is no need to perform work such as marking thesurface of the concrete W, as opposed to when rebar is detected using aconventional metal detector provided separately from the handheld powertool.

As a result, the work from the detection of the rebar W1 to the workingof the concrete W will be easier than in a conventional case.

Furthermore, since the metal detector 20 notifies the operator ofwhether or not there is rebar W1 by controlling the lighting of the LEDs24 b of the display unit 24, the metal detector 20 is easier to use in anoisy work environment than a conventional metal detector that notifiesthe operator with a warning sound.

Also, since the metal detector 20 is mounted in an integrated state onthe distal end side of the handheld power tool 10, the work can becarried out continuously, from the detection of the rebar W1 to theworking of the surface.

Furthermore, in this embodiment, if the metal detector 20 determinesthat rebar W1 is present, the color, number, etc., in which the lightsare lit and displayed on the LEDs 24 b of the display unit 24 arechanges in stepwise fashion according to the distance to the rebar W1.

Consequently, on the surface of the concrete W, for example, the levelcan be set stepwise from the drive permission area to the driveprohibition area.

Here, the LEDs 24 b showing the determination result for the presence orabsence of rebar W1 in the metal detector 20 are disposed so as to facethe inside diameter side of the substantially annular metal detector 20(the tip tool 18 a side of the handheld power tool 10).

This reduces the burden on the operator's eyes due to direct viewing ofthe light source, and because white light can be turned on during workusing the handheld power tool 10, the place where the operator isworking can be brightly illuminated to ensure better visibility.

The metal detector 20 can also be used alone, and the drilling work andmetal detection can be performed in parallel.

Embodiment 2

A handheld power tool 100 according to another embodiment of the presentinvention will now be described with reference to FIGS. 16 to 19.

The handheld power tool 100 in this embodiment differs from Embodiment 1above in that the dust collecting unit 40 is not attached to the mainbody 11, and the metal detector 20 is attached via a holder 101. In thisembodiment, those components that are the same components as in thefirst embodiment are numbered the same and will not be described again.

As shown in FIG. 16, the handheld power tool 100 of this embodiment doesnot have the dust collecting unit 40 of the first embodiment, and themetal detector 20 is attached to the distal end side via the holder 101.

As shown in FIG. 16, the holder 101 is attached to the distal end sideof the main body 11 in order to integrate the main body 11 of thehandheld power tool 100 with the metal detector 20. As shown in FIG. 17,the holder 101 has a telescoping beam 101 a, a sensor holding portion101 b, a fixing portion 101 c, a harness opening 101 d, and a gripfixing portion 101 e.

The telescoping beam 101 a is a member that can be expanded andcontracted toward the distal end side with respect to the main body 11,and a bellows member 102 through which a harness (not shown) is passedis disposed inside the concave shape.

This allows the length of the telescoping beam 101 a to be adjusted tothe proper length to match the length of the tip tool 18 a, for example,and the telescoping beam 101 a is extended when the tip tool 18 a is tobe attached to or detached from the tip portion 18, for example, whichmakes replacement much easier.

The sensor holding portion 101 b is provided on the front end side ofthe holder 101, and the metal detector 20 is mounted from the rear endside.

The fixing portion 101 c is a portion for fixing the holder 101 to themain body 11 of the handheld power tool 100, and the tip portion 18 ofthe main body 11 is inserted into the substantially annular portionthereof.

The harness opening 101 d is an opening provided at the rear end of theholder 101, and a harness (not shown) is routed out of the metaldetector 20 through the bellows member 102.

The grip fixing portion 101 e is a member for fixing the grip portion 11a, and is provided so as to extend in a direction substantiallyperpendicular to the lengthwise direction of the holder 101.

The handheld power tool 100 in this embodiment is used in a state inwhich the metal detector 20 is integrated with the main body 11 via theholder 101.

This affords the same effect as that of the first embodiment.

Here, the handheld power tool 100 of this embodiment may be a handheldpower tool 200 configured such that the metal detector 20 retracts fromthe position being worked by the tip tool 18 a after the determinationof the presence or absence of rebar W1 by the metal detector 20.

That is, as shown in FIGS. 18A and 18B, with the handheld power tool200, when the metal detector 20 disposed at the distal end of the holder101 is rotated (moved) downward, the metal detector 20 is retracted fromnear the tip tool 18 a of the handheld power tool 200 so that drillingwork can be performed.

A retracting mechanism 203 for retracting the metal detector 20 downwardis provided near the connected portion between the main body 11 and aholder 201, and includes a wire 203 a as shown in FIG. 18A.

The metal detector 20 is attached from the rear end side to a sensorholding portion 201 b of the holder 201.

A contact detector (contact detection unit) 202 for detecting contactwith the surface of the concrete W is provided on the distal end side ofthe sensor holding portion 201 b.

The contact detector 202 is, for example, a strain sensor or aphotosensor, is attached to the surface of the sensor holding portion201 b on the distal end side via the spring 202 a, and is biased towardthe distal end side. Also, when the contact detector 202 comes intocontact with the surface of the concrete W, the spring 202 a contractsto effect a change from the OFF state to the ON state.

Also, as shown in FIG. 19, the contact detector 202 is provided as acomponent of the metal detector 20. When contact with the concrete Wsurface is detected, the retracting mechanism 203 moves the metaldetector 20 to the retracted position.

At this point, in the normal state, the contact detector 202 is biasedaway from the metal detector 20 by the biasing force of the spring 202a. Accordingly, tension is also applied to the internal wire 203 a, andthe horizontal state of the holder 201 is maintained (see FIG. 18A).

Then, when the handheld power tool 200 is pressed against the surface ofthe concrete W during drilling work or the like, the spring 202 a iscompressed and the tension of the wire 203 a inside is also relaxed,causing the metal detector 20 to rotate downward and out of the way,along with the holder 201, under the force of gravity (see FIG. 18B).

As a result, when work is performed on the concrete W using the tip tool18 a, it is possible to reduce the load, such as the exposure of themetal detector 20 to dust and the application of vibration.

When the handheld power tool 200 is moved away from the surface of theconcrete W at the end of the work, the contact detector 202 is againbiased away from the metal detector 20 by the biasing force of thespring 202 a, tension on the internal wire 203 a is also restored alongwith this, and the metal detector 20 returns to its normal position.

In this embodiment, an example was given in which the retractingmechanism 203 was operated when the contact detector 202 came intocontact with the surface of the concrete W, but a push button switch orthe like may be manually operated to retract the metal detector 20 fromthe distal end side of the handheld power tool 10, for example.

Also, the initialization processing unit 37 may perform initializationprocessing when the contact detector 202 detects contact with thesurface of the concrete W.

OTHER EMBODIMENTS

An embodiment of the present invention was described above, but thepresent invention is not limited to or by the above embodiment, andvarious modifications can be made without departing from the gist of theinvention.

(A)

In the above embodiment, an example was given in which the presentinvention was realized as the metal detector 20 and as a metal detectionmethod in which this metal detector 20 was used. However, the presentinvention is not limited to this.

For instance, the present invention may be realized as a metal detectionprogram that causes a computer to execute the above-mentioned metaldetection method in which this metal detector is used.

This metal detection program is stored in a memory (memory unit)installed in a handheld power tool, and a CPU reads the program storedin the memory and causes the hardware to execute the various steps. Morespecifically, the same effect as above can be obtained by having the CPUread the metal detection program and execute the above-mentioneddetection signal acquisition step, determination step and displaycontrol step.

The present invention may also be realized as a recording medium onwhich this metal detection program is stored.

(B)

In the above embodiment, an example was given in which a plurality ofrotatable rollers 46 a were provided on the contact surface 46 formed onthe distal end side of the metal detector 20. However, the presentinvention is not limited to this.

That is, it is preferable for the contact surface with the concretesurface to be configured or to undergo treatment so as to reducefrictional resistance, in order to make the work easier when scanningthe metal detector over the concrete surface to detect rebar.

For instance, as shown in FIG. 20A, a metal detector 121 may have asurface treated portion 121 a (for reducing friction) formed on the sidethat comes into contact with the concrete.

Also, as shown in FIG. 20B, a metal detector 122 may be provided with aplurality of balls 122 b that rotate while in contact with the surfaceof the concrete, on a surface 122 a that is on the side in contact withthe concrete.

Furthermore, as shown in FIG. 20C, a metal detector 123 may be providedwith two roller portions 123 b that rotate while in contact with thesurface of the concrete, on a surface 123 a that is on the side incontact with the concrete.

With all of the above configurations, the metal detector can be movedsmoothly over the concrete surface, which makes the work easier.Furthermore, the durability of the metal detector can be improved if themetal detector is not brought directly into contact with the concrete.

(C)

In the above embodiment, an example was given in which the operator wasnotified of the detection result for the rebar W1 by the metal detector20 by lighting in three colors of green, yellow, and red. However, thepresent invention is not limited to this.

For instance, the means for notifying of the detection result by themetal detector need not be expressing the result with light of differentcolors as in the above embodiment, and may instead be some other means,such as text information or voice information.

Also, in the above embodiment, an example was given in which theoperator was notified of the approach (presence or absence) of metal byusing three colors of light, but the operator may instead be notified ofthe approach of metal by using light of two colors or of four or morecolors.

(D)

In the above embodiment, an example was given in which the operator wasnotified of the detection result for the rebar W1 by the metal detector20 by lighting the eight LEDs 24 b in a plurality of different colors.However, the present invention is not limited to this.

For instance, the display unit for turning on the lamps is not limitedto eight LEDs, and seven or fewer, or nine or more LEDs may be used, ora light source other than LEDs may be used.

(E)

In the above embodiment, an example was given of a method for detectingrebar contained in concrete, in which an inductive type of metaldetector was used that sensed the impedance of a detection coil, whichchanges with the eddy current generated in the metal (the object to bedetected) as the metal approaches the magnetic field generated bypassing a current through the coil included in the detector unit.However, the present invention is not limited to this.

For instance, a metal detector that employs some other method may beused, such as a capacitance type that senses changes in capacitanceproduced between the detector and the metal to be detected, or ahigh-frequency oscillation method that detects non-ferrous metal such asaluminum.

(F)

In the above embodiment, an example was given in which impedance changesin the winding coil 22 b wound around the detector unit 22 were detectedto detect the presence or absence of the rebar W1. However, the presentinvention is not limited to this.

For instance, a pattern type coil may be used instead of a wound coil todetect the changes in impedance and detect the metal.

(G)

In the above embodiment, an example was given in which theinitialization processing of the detection result by the metal detector20 either involved control performed depending on sensing theorientation of the handheld power tool 10, or was performed by pressingthe reset switch 19. However, the present invention is not limited tothis.

For instance, the initialization processing of the detection result bythe metal detector may be configured so that only one of the above twocontrols can be performed, or initialization processing may be performedby some means other than the above two controls, such as a level gauge.

Also, the position of the reset switch used to perform initializationprocessing is not limited to the position described in the aboveembodiment, and this reset switch may instead be provided at some otherposition in the handheld power tool or the metal detector.

(H)

In the above embodiment, an example was given in which the metaldetector 20 was used in a state where it could be attached to anddetached from the main body 11 of the handheld power tool 10. However,the present invention is not limited to this.

For instance, the metal detector may be configured to be integrated withthe main body of the handheld power tool in a non-detachable state.

(I)

In the above embodiment, an example was given in which concrete in whichrebar was embedded served as the target to be subjected to work with thehandheld power tool 10. However, the present invention is not limited tothis.

For instance, the target may be drywall or another such wall material,and the handheld power tool may be one that performs any of varioustypes of work while metal contained in the wall material is beingdetected.

Also, the metal in the target is not limited to being rebar, and mayinstead be some other metal member, such as a frame or a bolt.

(J)

In the above embodiment, an example was given in which the presentinvention was applied to a hammer drill as an example of the handheldpower tool to which the metal detector 20 was attached. However, thepresent invention is not limited to this.

For instance, the handheld power tool to which the metal detector of thepresent invention is mounted may be some other handheld power tool, suchas an impact drill or a vibration drill.

INDUSTRIAL APPLICABILITY

The metal detector of the present invention has the effect of allowingan operator to be notified of the presence or absence of metal inside atarget such as concrete, without coming into contact with the metal, andtherefore can be widely applied to various work tools that perform workwhile detecting metal.

1. A metal detector that detects metal contained in a target and is removably attached to a handheld power tool that is used to work on the target, the metal detector comprising: a mounting portion that is mounted on a distal end part of the handheld power tool; a detection signal acquisition unit configured to acquire a detection signal which changes according to a detection intensity of the metal contained in the target; a determination unit configured to determine a presence or absence of the metal on the basis of an acquisition result acquired by the detection signal acquisition unit; a display unit configured to display the presence or absence of the metal by turning on different lights; and a display control unit configured to control so as to switch a color of a light displayed on the display unit on the basis of a determination result from the determination unit.
 2. The metal detector according to claim 1, further comprising a prohibition signal transmission unit configured to transmit a drive prohibition signal for prohibiting drive of the handheld power tool when it has been determined by the determination unit that the metal is present.
 3. The metal detector according to claim 1, further comprising a permission signal transmission unit configured to transmit a drive permission signal for permitting drive of the handheld power tool when it has been determined by the determination unit the metal is absent.
 4. The metal detector according to claim 1, wherein the display control unit controls the display unit so as to emit an auxiliary light that illuminates a portion to be worked by the tip tool that will work the target, while the handheld power tool is being driven.
 5. The metal detector according to claim 4, wherein the display control unit controls the display unit so as to emit white light as the auxiliary light.
 6. The metal detector according to claim 1, wherein the determination unit determines the presence or absence of the metal by comparing the acquisition result acquired by the detection signal acquisition unit with a specific threshold value.
 7. The metal detector according to claim 1, further comprising: an orientation sensing unit configured to sense an orientation of the handheld power tool; and an initialization processing unit configured to initialize a result acquired by the detection signal acquisition unit when the orientation sensing unit has sensed that the handheld power tool is in a specific orientation.
 8. The metal detector according to claim 1, further comprising: a contact portion having a roller portion configured to come into contact with the target and rotate in a movement direction of the handheld power tool in a state of being in contact with the target.
 9. The metal detector according to claim 1, further comprising: a contact portion having a friction reducing portion configured to come into contact with the target and reduce a friction generated between the target and the contact portion.
 10. The metal detector according to claim 1, further comprising: a contact detection unit configured to detect a contact with the target.
 11. The metal detector according to claim 10, wherein the contact detection unit is a contact switch configured to change from an OFF state to an ON state upon coming into contact with the target.
 12. The metal detector according to claim 10, further comprising: a retracting mechanism configured to retract the metal detector from the distal end part of the handheld power tool when the contact detection unit has detected a contact with the target.
 13. The metal detector according to claim 1, further comprising: a dust collecting unit configured to draw in an outside air around the distal end part of the handheld power tool.
 14. The metal detector according to claim 13, wherein the dust collecting unit is detachably attached to the distal end part of the handheld power tool.
 15. A handheld power tool, comprising: the metal detector according to claim 1; a distal end part to which the metal detector is mounted; a drive unit configured to rotationally drive a tip tool for working the target; and a drive control unit configured to control a drive of the drive unit.
 16. A metal detection method that makes use of a metal detector that detects metal contained in a target and is removably attached to a distal end part of a handheld power tool that is used to work on the target, the method comprising: a detection signal acquisition step in which a detection signal acquisition unit of the metal detector acquires a detection signal that changes according to a detection intensity of the metal in the target; a determination step in which a determination unit of the metal detector determines a presence or absence of the metal on the basis of an acquisition result acquired by the detection signal acquisition unit; and a display control step in which a display control unit of the metal detector controls so as to switch a color of a light displayed on the display unit on the basis of a determination result by the determination unit.
 17. A metal detection program that causes a computer to execute a metal detection method that makes use of a metal detector that is removably attached to a distal end part of a handheld power tool that will perform work inside a target, the method comprising: a detection signal acquisition step in which a detection signal acquisition unit of the metal detector acquires a detection signal that changes according to a detection intensity of the metal in the target; a determination step in which a determination unit of the metal detector determines the presence or absence of the metal on the basis of an acquisition result acquired by the detection signal acquisition unit; and a display control step in which a display control unit of the metal detector controls so as to switch a color of a light displayed on the display unit on the basis of a determination result by the determination unit. 